Method of making a heat exchanging element



I April 119397 5 A. BERG ETAL 2,155,395

I METHOD OF MAKING A HEAT EXCHANGCINGL ELEMENT Filed Aug. 4, 1937JNVENTOR ALF/FED J 55% BY JOHN, 0. H085 ATTORNEY Patented Apr. 25, 1939UNITED- STATES METHOD OF MAKING A HEAT EXCHA NGING ELEMENT Alfred J.Berg, Portsmouth, N. H., and John 0. Huse, United States NavyApplication August 4, 1937, Serial No. 151,379

Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) Our present invention relates to a new and useful heat orcold exchanging element and method of making the same, which element maybe otherwise usefully employed.

5 This invention is a continuation in part of and an improvement uponour application, Serial No. 63,894, series of 1935, entitled Heatexchanging element and process of making the same, filed February 14,1936, as well as upon our like-entitled application, Serial No. 63,897,series of 1935, filed February 14, 1936, and in application No. 157,378filed herewith. In all of said filed applications the ribs or fins ofheat exchanging elements are machined or cut as a shaving from one endof a tubular bar of metal the size of whose opening substantiallyconforms to the opening through the fin shaved from said bar, while theoutside dimension of said tubular bar conforms to the outside dimensionof the shaved helical fin. In the first and last enumerated of saidapplications a helical heat exchanger rib or fin is cut by differentmethod and means from the end of a bar. Our present inventionsubstantially improves the shaved helical fin as well as cheapensitsproduction, increases the length of the helical shaved fin that may besevered without breakage, dispenses with the necessity of shaving thehelical fin from a tubular bar by cutting the same from a solid bar ofmetal simultaneously with the shaving or machining fin strip to auniform width of fin or rib, in which operation a solid central bar ofmetal is formed with a machined exterior surface which substantiallyvibrationlessly' supports the portion of the helical fin which has beensevered from the original bar, and which central smaller bar may be usedfor other purposes after the originally larger bar has been worked upinto two products, 40 one of which is the helical fin and the other ofwhich being the central smaller bar which supports and enables a muchlonger helical fin to be severed without breakage from the larger bar.

Other objects and. accomplishments of our present invention will morefully appear in the specification. I

In the drawing, Fig. 1 is a side elevation view of one form ofcutterwhich we have advantageously employed in the attainment of the objectsand advantages of our present invention;

- Fig. la is an end view of the tool shown in Fig. 1;

Fig. 1b is a side elevation view of a somewhat different cutter which wehave advantageously employed in the attainment of the objects and ad-'vantages of our present invention;

Fig. 1c is an end view of the tool shown in Fig. 1b;

Fig. id is a perspective view of the tip portion 5 of an improvementupon either of the cutting tools shown in Figs. 1 or 112;

Fig. 1c is a tip end view of the tool shown in Fig. 1d;

Fig. 2 is a top plan view of a bar of metal 10 mounted in a lathe orsimilar turning machine tool provided with a turning tool similar toeither Figs. 1 or 117; and, I

Fig. 3 is a view similar to Fig. 2 but showing the turning tool ofeither Figs. 1 or lb made in 15 accordance with Fig. 1d and producing ahelical shaved fin whose inner edge extends laterally from the planeoccupied by the remainder of the helical fin;

Fig. 4 is a plan view in partial cross-section of 20 a portion of a heatexchanger tube or element made in accordance with our present inventionwith its fin or rib as formed in accordance with Fig. 2. i

Fig. 5,isa view similar to Fig. 4 but showing 25 its rib or fin as madein'accordance with Fig, 3;

and

Fig. 6 is an enlarged cross-sectional view of a rib as made inaccordance with Fig. 3.

In the drawing, in which like characters of 30 of the inner and outeredges of the helical shaved reference denote the same parts m dla'gram'matically represents the chuck of a lathe or other turning tool adaptedto rigidly hold a relatively long bar ll of solid metal concentric withspindle l2, Fig. 2 of the lathe or like machine tool. 35 I3 representsthe tool post portion of the usual carriage Ba 0? the machine tool whichis advanced longitudinally of the bar II by the usual screw feed whichis so well known that it need not be illustrated. The tool post I3 isbifurcated to 40 receive the shanks of cutting tools l4 and [5 which aresecured, in said bifurcation by the screw IS. The turning tool 14 is theordinary tool usually employed to true up the periphery of a cylinder;while the cutting tool 15 is the tool 45 illustrated in Figs. 1b, 1c orin 1d, 1e, 1f of the drawings of our last stated previously filedapplication, with the exception of the tip of the cutter. This tip, inour last stated previously filed application, projects into the hollowbore 5 of the tubular bar of metal from which the' helical -fin isshaved or turned, and consequently such tip is required to perform nofunction other than to insure the" complete severance of the helical finfrom the tubular bar. The shearing 55 cutting end of the tool I in asurface 17h which, when in use, extends approximately at a tangent tothe inner diameter of the helical fin strip. The surface I'Ih may extendto the bottom of the tool, or it may extend only a portion of suchdistance, as in Figs. l,la, with the lower portion of such distancecomprising a surface IIi extending from the lower end of the surfaceI'Ih thence downwardly and toward the opposite end of the tool I5 toafford a more pronounced clearance for the surface IIh. The shearingedge I1, which forms the lateral surfaces of the' helical fin severedfrom the bar II, intersects at the outer end of the tool I 5 with ashearing edge I17 coinciding with the hypotenuse of the angular surfacecomprising the surface IIh. This shearing edge I17 is formed by thegrinding of thesurface I'lh upon the end of the tool I5 at greater thana right angle from said edge I17. In the making of the helical fin theshearing edge ll of the tool I5 cleaves the lateral surfaces of thehelical rib or fin Ila from the solid metal of the solid bar II whilethe shearing edge I Ii shears the inner edge of the fin or rib I la fromthe bar II and leaves the rigid central bar Ilb, whoseouter diameter isturned to aguniform diameter by the shearing edge of the cutting toolI4, coincident with the separation from the bar I I of the rib or finIIa. As the helical rib or fin Ila is separated from the bar of metalII, the inner edge of the separated helices of the strip of the rib orfin Ila are supported by the central bar Ilb, which is all that remainsof the original bar II after the helical rib or fin Ila has been severedtherefrom.

In the turning of the helical rib or fin, in accordance with the firstand last of the previously stated applications for Letters Patent, themajor problem was to obtain the shaving as long as possible by avoidingthe breakage thereof. While satisfactory results were obtained by a verysubstantial length of shaved helical fin being produced before the samebroke, we have found that the vibration of the unsupported helical finbeing rapidly turned about its longitudinal axis in the severing of thehelical fin from the tubular bar of metal substantially contributed tothe breakage of the helical rib or fin into shorter lengths than couldbe made from the total length of the bar II. In solving this problemapplicants have heretofore provided the usual lathe or turning machinetool with a ro or tube to receive there- I in the helical 'cut finmmediately after it was severed from the bar and hold the severed finconcentric with the bar from which it was severed as well assubstantially free from vibration. For the same purpose we have alsoheretofore provided such machine tools with a rod at least whoseadjacent end was mounted concentric with the bar of metal from which thehelical fin was being removed. The removed helical fin would surroundthis rod which would 'revolvably hold the severed helical finsubstantially free from vibration which would tend to break the same. Bythese practices we have heretofore obtained substantially longer helicalfins thanwas theretofore producible. However, the tube or rod-attachmentto or association with the usual turning machine tool was unfamiliarpractice and objectionable to those required to use such tools in theproduction of the shaved helical rib or fin. Furthermore, the frictionalengagement of the'outer or the inner diameters of the severed helicalfin respectively with such tube or rod,

- Thecentral bar llb, which is rigid with the unshaved or unturnedportion of the main bar II, not onlyvibrationlessly supports the helicesof the helical ribs or fins IIa separated from the bar II, but also saidbar Ilb turns concentrically with the severed portion of the helical ribor fln Ila so that there is not even frictional disturbance between therigid bar I Ib and the separated portion of the helical fin Ila. Byreason of this vibrationless as well as frictionless support of thesevered portion of the helical fin or rib Ila we have been able toproduce a substantially longer severed helical fin than has beenheretofore possible commercially. Furthermore, the same is produced in amanner which adds no extraneous tube or rod to the turning machine, andwe obtain the shaved fin with greater facility and without inconvenienceto those customarily operating such machines. Further than this, the barI Ib may-be conveniently kept associated with the sheared helical finuntil the same-is removed and placed upon heat or cold exchanging tubeor member 20, after which the solid bar Ilb may be employed for othercommercial purposes, for many ofwhich the same is more desirable byreason of its turned exterior surface as distinguished from the drawn orrolled surface heretofore usual in such bars of metal.

These helical fins or ribs Ila are associated with the heat or coldexchanging tube or member 20 of Fig. 2 in any desirable or. convenientmanner in accordance with the joint or several previous inventions ofapplicants or either of them.

As shown in Fig. 2 the cutting tool II is mounted in the tool post l3substantially parallel with and on one side of the cutting or turningtool I5. The outer end of tool I4 is provided with a cutting edge whichturns true and concentric the outer surface of the bar II, so that thewidth of the metal comprising the helices of the helical rib or fin Ilais uniform and that its exterior and interior diameters are concentricwhen and as severed from the bar I I, and are so maintained throughouttheir association with the bar IIb because the helical ribs or fins IIaare subjected to no stress relative to the bar IIb.

In Fig. 1d the bevelled side of cutter I5 at a point comprising thejunction of cutting edges I1 and I1 is provided with a more bluntlybevelled recess I'lm, Figs. 1a and 1e. This recess results in thelateral projection of the inner edge of the helical rib or fin I la.This lateral projection, 0, Fig. 3, is of substantially the samethickness of metal as the remaining portions of the rib or fin Ila. Thelateral projection He is formed progressivelyby the like progressionbetween the tapering surfaces of the turning tool l5 forming the cuttingedge I1 and the terminal bevel IIm at the outer point of the tool I5,which terminal bevel forms the upper portion of shearing edge I11 in thetool illustrated in Figs. 1d and 1e.

The helical fin I la producedln accordance with the tool heretoforedescribed andv illustrated in Figs. 1a, 1e and 1) may be secured aboutor otherwise associated with the heat or cold exchanging tube 20a inaccordance with any of the heretofore joint or several inventions of.the applicants or in any other convenient or desirable manner asgenerally indicated inFig. 4.

The shearing edge I17 of Figs. 1a, 10 and 16 which simultaneously formsthe inner turned bore of the helical fin as well as the exterior turnedsurface of the supporting core bar llb, extends longitudinally outwardfrom the bar H in the direction in which the helical rib is projectedupon its progressive severance from the solid bar. Such cutting edge oredges I1, I17 occasion a substantial shearing out which results in asubstantial angular fiowage of portions of the metal at the severedinner metal of the severed inner surface forming the bore of the helicalfin. Such fiowage affords a substantial cold working of the inner edgeof the helical rib or fin which engages the outer periphery of the heatexchanging tube or member 20 and affords increased heat exchangingcapacity due to such cold working. The cold working effect of the outingedges l! of the cutter I is stated in the first and last of thehereinbefore stated of our applications to which reference may be had tothe structure and functions of said cutting edges l1 with the sameefficiency as if the same were written at length herein.

The recess l'lm in the tip of cutting tool l5 inherently increases thebluntness of the beveled side of such tool as it recedes from the"-hearing edge H, which edge I! continues in a straight line, as shownmore clearly in Figs. 1e and 1 As the shearing edges I1, I19 of tool l5separate the lateral and inner surfaces of helical rib or fin llb frombar II and its resulting central portion l lb the metal comprising allbut the inner edge of rib or fin l lb fiows over the straight beveledside of tool l5 which forms such portions of rib or fin llb fiat, whilethe inner edge of rib or fin llb fiows down into and-then out of theside of said recess llm and results in the formation of the curvedlateral projection llc, Figs. 3, 5 and 6. Such projection llc greatlyincreases the strength and freedomfrom deformation of therib or fin l lbas well as magnifies the area of its heat exchange contact with theelement 200', while the cold working manner of the formation of saidprojection llc increases the density of its constituent metal with itsattendant increase in its rate of heat exchange and increases saidstrength and freedom. Such projection He may grip the outer surface ofthe element 20a when the same is substantially circular and affordsufiicient securement thereto or facilitate such securement. Thisconstruction of the rib or fin llb enables thinner metal to be usedtherein of practically any desired height above the element 20 uponwhich they may be mounted without impairing the strength and stabilityof the rib or,

fin. This'also enables a greater number of ribs or fins to be used perunit of length of said element 20, and greatly decreases the weight andcost oi."

a heat exchanger of any given heat exchanging capabity.

In the production of the rib or fin Ila according to our invention, asheretofore explained,

other than made by cutter "(the rib or fin llb is the only cutting fromthe bar ll ,since no shaving or shavings are necessary other than therib or fin llb. r

In turning the helices of the helical rib or fin Ha from a tubular barof metal, when the external and internal diameters of such helices areunmachined, the difi'erent helices are not invariably concentric. .Thisoccasions some production problems where pressure is desired tobeapplied to the edge of the outer periphery of the helices,

and/or where a physical uniform continuous contact is re-requiredbetween the tube or body 20 and the inner edge of the rib or fin and acontinuously uniform space is desired about the outer edge of said ribor -fin. We have overcome such production problems by, simultaneouslywith the production of the rib or fin, turning the interior and exteriordiameters of the helices which also affords greater heat conductivecapacity to the rib or fin, as well as therefrom to the tube or body 20.Such turning of the helical rib or fin, including all of its edges, alsodispenses with the multiple production problems of making the rib or finof a fiat metal strip bent edgewise into helices or by precoiling inpart or in whole before being applied about the body 20 in which suchbending could not be accom-.

plished even with copper strips of awidth substantially'in excess ofone-halfof the diameter of the tube or body 20 without precoiling andfor the Government of the United States for governmental purposeswithout the payment of any royalty thereon or therefor; I

Having now so fully described our invention;

that others may therefrom make and use the same, what we claim is:

1. The method of making an apertured helical heat exchange fin,comprising progressively cutting a bar of heat conductive metalcontinuously at its end and in the direction of its length to a depththat leaves an uncut portion of the bar to directly form by the cuttingoperation an apertured helical heat exchange fin, simultaneously as apart of the aforesaid cutting operation severing the fin at its innerperiphery from the uncut portion of the bar, and supporting theapertured helical heat exchange fin thereon during the cuttingoperation.

2. The method of making an apertured helical heat exchange fin,comprising progressively and substantially uniformly cutting a bar ofheat conductive metal continuously at .its end and in the direction ofits length to a depth that leaves an uncut portion of the bar todirectly form by the cutting operation an apertured helical heatexchange fin having a substantially uniform thickness throughout 'and aheight equal to many times its thickness, simultaneously as a part ofthe aforesaid cutting operation severing the fin at its'inner peripheryfrom the uncut portion'of the bar, and supporting the apertured helicalheat exchange fin thereon duringthe cutting operation.

3.1The method of making an apertured heliapertured helical heat exchangefin on the aforesaid uncut portion of the bar during the cuttingoperation.

4. The method of making a heat exchange device including a heat exchangeelement provided with a helical heat exchange fin secured thereto,comprising progressively cutting a. bar of heat conductive metalcontinuously at its end and in the direction of its length to a depththat leaves an uncut portion of the bar to directly form by the cuttingoperation an apertured helical heat exchange fin, simultaneously as apart of the aforesaid cutting operation severing the fin at its innerperiphery from the uncut portion of the bar, supporting the aperturedhelical heat exchange fin thereon during the cutting operation,positioning the fin thus formed about a heat exchange element andsecuring the fin thereto.

5. The method of making a heat exchange device including a heat exchangeelement provided as a part of the aforesaid cutting operation severingthe fin at its inner periphery from the uncut portion of the bar andforming thereat a "lateral projection, supporting the apertured helicalheat exchange fin on the aforesaid uncut portion of the bar during thecutting operation,

positioning the fin thus formed about a heat exchange element with itslateral projection in contact with the surface thereof, and securing thefin thereto.

JOHN O. HUSE. ALFRED J. BERG.

